I usually do not prepare much (besides trying to add some extra minerals), but I suspect that I should. I mean it sounds reasonable that the bowl/intestines should be as empty as possible when going into a fast, just have not figured out how to accomplish that without like using a salt water flush (do not want to do that, I feel terribly bloated from all the salt and water almost at once and the “flush” itself) or doing an enema right before the start. I mean - sounds like you could get dehydrated and very uncomfortable. So the solution is likely to eat easily/fast digested food just before the fast and/or doing a very short water fast just like 4 hours before going into the dry fast? Feel free to fill in if you know a better strat.
Secondly there is the liver + kidney detoxes you are supposed to do, but I do not quite buy that you can get any bigger results regarding liver detox by eating pills and drinking tea than you get from the fast itself. Active coal could be reasonable though, I think?
Regarding vegetarian diet; especially some meat can for some people be really hard to digest. Also I am guessing all the fibers and vitamins from the fruit/vegetables count for something regarding overall health during the start. But these are just guesses, dr F does not really specify why. If you have some kinda plan where these factors fit in with meat then I would say go for it. But I am no doctor so do not listen to me, lol!
I typically eat keto unless special occasions but I find going carnivore a day before really helps… Also OMAD the day before if I’m not currently doing it already (typically am). Sea salts and minerals before hand occasionally too